# Reciprocity

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**Reciprocity** may refer to:

- Reciprocity (Canadian politics), used to describe the concept of free trade with the United States of America
- Reciprocal trade agreement, entered into in order to reduce (or eliminate) tariffs, quotas and other trade restrictions on items traded between the signatories

- Reciprocity (photography), the relationship between the intensity of the light and duration of the exposure that result in identical exposure
- Traffic violations reciprocity where non-resident drivers are treated like residents
- Reciprocity (
*Fringe*), a 2011 episode of the television series*Fringe*

## Social sciences and humanities

- Norm of reciprocity, social norm of in-kind responses to the behavior of others
- Reciprocity (cultural anthropology), way of defining people's informal exchange of goods and labour
- Reciprocity (evolution), mechanisms for the evolution of cooperation
- Reciprocity (international relations), principle that favours, benefits, or penalties that are granted by one state to the citizens or legal entities of another, should be returned in kind
- Reciprocity (social and political philosophy), concept of reciprocity as in-kind positive or negative responses for the actions of others
- Reciprocity (social psychology), in-kind positively or negatively connotated responses of individuals towards the actions of others
- Ethic of reciprocity (the Golden Rule), one should treat others as one would like others to treat oneself
- Serial reciprocity, where the benefactor of a gift or service will in turn provide benefits to a third party

## Natural sciences

- Reciprocity (engineering), used in the analysis of structures and to resolve complex load conditions
- Reciprocity (electromagnetism), theorems relating sources and the resulting fields in classical electromagnetism
- Reciprocity (network theory), theorem about transfer function of passive networks
- Reciprocity in network, measures the tendency of vertex pairs to form mutual connections between each other
- Reciprocity of twist and wrench, in screw theory
- Reciprocity theorem (disambiguation), several unrelated results
- Antenna_(radio)#Reciprocity, in transmitting and receiving

## Mathematics

- Reciprocity law in mathematics, including
- Quadratic reciprocity, a fundamental result in number theory
- Cubic reciprocity, theorems that state conditions under which the congruence
*x*^{3}≡*p*(mod*q*) is solvable - Quartic reciprocity, a collection of theorems in elementary and algebraic number theory that state conditions under which the congruence
*x*^{4}≡*p*(mod*q*) is solvable - Artin reciprocity law, a general theorem in number theory that provided a partial solution to Hilbert's ninth problem
- Reciprocity relation or
*exact differential*, a mathematical differential of the form*dQ*, for some differentiable function*Q*

- Weil reciprocity for algebraic curves
- Reciprocal polynomials, the coefficients of the remainder polynomial are the bits of the CRC
- Reciprocal square root
- Reciprocity (projective geometry), a collineation from a projective space onto its dual space, taking points to hyperplanes (and vice versa) and preserving incidence
- Frobenius reciprocity, from group representation theory
- Reciprocity law for Dedekind sums
- Stanley's reciprocity theorem, states that a certain functional equation is satisfied by the generating function of any rational cone and the generating function of the cone's interior
- Hermite reciprocity for invariants of binary forms.

## Place

- Reciprocity No. 32, Saskatchewan, rural municipality in Canada

## See also

- Reciprocal (disambiguation)
- Reciprocation (disambiguation)
- Reciprocity Treaty (disambiguation)
- Mutual assent in contract law, sometimes called reciprocity
- Symbiosis, an interaction between two organisms living together in more or less intimate association
- Double standard, the unjust application of different sets of principles for similar situations
- Hypocrisy, the state of pretending to have virtues, moral or religious beliefs, principles, etc., that one does not actually have

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